Vehicle-mounted information device

ABSTRACT

An information device for on-vehicle use, includes: a CPU which is capable of normal operation and of standby operation which achieves low power consumption; a first power supply for use during the normal operation of the CPU; a second power supply for use during the standby operation of the CPU; and a power control device which performs ON-OFF control of the first power supply and the second power supply. And the CPU outputs a first signal to the power control device when the CPU transits from the normal operation to the standby operation; the power control device outputs a second signal to the second power supply which turns the second power supply ON when the first signal has been inputted from the CPU, and outputs a third signal to the first power supply which turns the first power supply OFF after a predetermined time period has elapsed after the output of the second signal; the CPU outputs a fourth signal to the power control device when the CPU transits from the standby operation to the normal operation; and the power control device outputs a fifth signal to the first power supply which turns the first power supply ON when the fourth signal has been inputted from the CPU, and outputs a sixth signal to the second power supply which turns the second power supply OFF after a predetermined time period has elapsed after the output of the fifth signal.

TECHNICAL FIELD

The present invention relates to an information device for on-vehicleuse.

BACKGROUND ART

In the prior art, with an information device for on-vehicle use such as,for example, a car navigation device, when the ignition key of thevehicle is turned OFF (i.e. has been rotated from the ACC position tothe OFF position), all the power which is being supplied to the carnavigation device has been turned OFF after certain predeterminedrequired information has been saved in non volatile memory or the like.Next, when the ignition key is turned ON (i.e. has been rotated from theOFF position to the ACC position or to the ON position), the powersupply to the car navigation device is turned ON, and, after theprevious required information has been read out from the non volatilememory and a predetermined setup procedure has been performed based uponthis information, the car navigation device is made available for use.

However, since a certain time period is required after the power supplyhas been turned ON for the reading out from the non volatile memory andfor the subsequent setup, it has been necessary to wait for aconsiderable waiting period until the car navigation device becomesavailable for use.

DISCLOSURE OF THE INVENTION

The objective of the present invention is to propose an informationdevice for on-vehicle use which includes a more suitable power controldevice, and which is made so as to be able to be used promptly after thepower supply has been turned ON, in its state before the power supplywas turned OFF.

In order to attain the above objective, an information device foron-vehicle use, comprises: a CPU which is capable of normal operationand of standby operation which achieves low power consumption; a firstpower supply for use during the normal operation of the CPU; a secondpower supply for use during the standby operation of the CPU; and apower control device which performs ON-OFF control of the first powersupply and the second power supply. And the CPU outputs a first signalto the power control device when the CPU transits from the normaloperation to the standby operation; the power control device outputs asecond signal to the second power supply which turns the second powersupply ON when the first signal has been inputted from the CPU, andoutputs a third signal to the first power supply which turns the firstpower supply OFF after a predetermined time period has elapsed after theoutput of the second signal; the CPU outputs a fourth signal to thepower control device when the CPU transits from the standby operation tothe normal operation; and the power control device outputs a fifthsignal to the first power supply which turns the first power supply ONwhen the fourth signal has been inputted from the CPU, and outputs asixth signal to the second power supply which turns the second powersupply OFF after a predetermined time period has elapsed after theoutput of the fifth signal.

In this information device for on-vehicle use, it is preferred that: aDRAM which is employed in the normal operation of the CPU and a thirdpower supply which supplies power to the DRAM are further provided; andwhen the CPU transits from the normal operation to the standbyoperation, the third power supply continues to supply power to the DRAM.

Also, it is preferred that: there is further provided an ON-OFFdetection device which detects a signal for turning the informationdevice for on-vehicle use ON and OFF in association with operation of anignition key of a vehicle; when the ON-OFF detection device has detecteda signal to turn the information device for on-vehicle use OFF, theON-OFF detection device notifies the CPU to an effect that the ON-OFFdetection device has detected the signal to turn the information devicefor on-vehicle use OFF; and the CPU transits to the standby operationafter having executed a predetermined procedure for standby. In thiscase, it is preferred that: when the ON-OFF detection device hasdetected a signal to turn the information device for on-vehicle use OFFdirectly before rotation of a starter motor of the vehicle, the ON-OFFdetection device notifies the CPU to an effect that the ON-OFF detectiondevice has detected the signal to turn the information device foron-vehicle use OFF directly before rotation of the starter motor of thevehicle; and the CPU transits to the standby operation after only aportion of the procedure for standby has been executed, so that theprocedure for standby is completed before starting of rotation of thestarter motor of the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a car navigation device according to anembodiment of the present invention.

FIG. 2 is a timing chart of the operation of a power supply etc. when aCPU transits into standby mode, and when the CPU transits into normalmode.

FIG. 3 is a figure showing the relationships between the position of anignition key and a signal ACC, a signal IGN, etc.

FIG. 4 is a figure showing a flow chart of the control when the standbymode is entered due to the signal ACC and the signal IGN.

FIG. 5 is a figure showing a flow chart of a transit procedure from thestandby mode to the power supply ON mode.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a block diagram of a car navigation device according to anembodiment of the present invention. The reference symbol 1 is a CPUwhich performs control of the car navigation device as a whole; thereference symbol 2 is a flash memory which is a non volatile memory; thereference symbol 3 is a DRAM which is a volatile memory; the referencesymbol 4 is a bus buffer, the reference symbol 5 is an ASIC, and thereference symbol 6 is a bus.

The ASIC 5 is made from gate arrays and comprises specialized logicelements. A present position detection device 10, a CD-ROM device 7, andan input device 8 are connected to the ASIC 5. The present positiondetection device 10 is endowed with the function of detecting thepresent ground position of the vehicle (the position of this vehicle),and may comprise, for example, an azimuth sensor (not shown in thefigures) which detects the azimuth of the movement of the vehicle, avehicle speed sensor (not shown in the figure) which detects the speedof the vehicle, and a GPS sensor (a GPS receiver) (not shown in thefigures) which detects GPS signals from GPS (Global Positioning System)satellites.

A CD-ROM 9 upon which road map data is recorded is loaded into theCD-ROM device 7, and the CD-ROM device 7 and the CD-ROM 9 constitute amap database device which is used for navigation. It should beunderstood that, if a CD-ROM for music or a program storage CD-ROM orthe like is loaded, it operates as a CD-ROM reading device. The inputdevice 8 consists of a keyboard or a joystick for input of a targetlocation for the vehicle and the like, or of various other switches.

A control program for the car navigation device is stored in the flashmemory 2, and further necessary information is stored as appropriate.The DRAM 3 operates as a work area or data area for the CPU 1 to executeits control program, and, for example, route search conditions orcalculation results of route searching, or map data which has beenreadout from the CD-ROM 9 or the like, are stored therein. Furthermore,the DRAM 3 also includes video RAM for a display device (not shown inthe figures) which stores image data for display. In other words, theDRAM 3 stores data which has been stored in the CD-ROM 9 or in the flashmemory 2 and has been read out, and stores calculation results whichhave been generated for use by subsequent further processing. The DRAM 3may, for example, employ S-DRAM (synchronous DRAM), and is capable ofprocessing at high speed.

With a car navigation device constituted in this manner, various typesof navigation are performed based upon the position information for thisvehicle which has been detected by the present position detection device10 described above and upon the road map data which is stored in theCD-ROM 9. For example, the road map in the vicinity of the presentposition of this vehicle and the position of this vehicle may bedisplayed upon the display device (not shown in the figures), and thedriver may be guided along a route (path) which has been obtained byroute searching.

Next, the power supply control (power control) of the car navigationdevice of this embodiment will be explained.

Before explaining the power supply control for the car navigationdevice, first, the electrical equipment system of the vehicle to whichthe car navigation device is fitted will be explained. The electricalequipment system of the vehicle is controlled by the ignition key switchbeing turned ON and OFF. Normally the key cylinder into which theignition key is inserted has a LOCK position, an OFF position, an ACCposition, an ON position, and a START position. When the ignition key isin the LOCK position or the OFF position, the electrical equipmentsystem such as the accessories and the like is not ON; while in the ACCposition, in other words in the accessory ON position, the power supplyto the accessories such as the car radio and the like is ON. Next, whenthe ignition key is rotated via the ON position to the START position,the starter motor is rotated and the engine is started. After this, therotation of the engine (its ignition) is maintained in the ON position.When from this state the ignition key is rotated to the ACC position,although the engine stops, the power supply to the accessories ismaintained as ON. Next, when the key is rotated to the OFF position, thepower supply to the accessories goes OFF; and, when it is rotated to theLOCK position, it is possible to remove the ignition key from the keycylinder with the steering in the locked state.

A signal ACC and a signal IGN as shown in FIG. 1 are inputted to the carnavigation device in association with the operation of the ignition keyswitch as described above. The signal ACC is ON when the ignition key isin the ACC position and in the ON position, and is OFF in the otherpositions thereof. The signal IGN is ON when the ignition key is in theON position and in the START position, and is OFF in the other positionsthereof. The ON and OFF of the supply of power to the car navigationdevice is controlled by these signals ACC and IGN.

The car navigation device of this embodiment has, as power supply modes,a power supply ON mode and a standby mode. The power supply ON mode is amode in which the supply of power is turned on to all the structuralelements of the car navigation device, and the processing for normal carnavigation is performed. And the standby mode is a mode in which the CPU1, the flash memory 2, the DRAM 3, and the bus buffer 4 are backed up bya predetermined power supply, while the supply of power to all the otherstructural elements is OFF. In other words, the standby mode is a modein which source power is supplied in a low power consumption mode toonly the minimum required level of components. The reason that thestandby mode is provided is in order to make it possible to use the carnavigation device promptly when next the device changes over to thepower supply ON mode, by maintaining the contents of the memory evenwhen the device enters the standby mode. An explanation of transiting tothe power supply ON mode and the standby mode by operation of theignition key will be provided later.

The car navigation device of this embodiment, overall, uses directcurrent power supplies of 5 VDC, 3 VDC, 1.8 VDC, and 2.5 VDC. Thereference symbol 11 is a power supply which generates 5 VDC and 3 VDCfrom the 12 VDC of the car battery. The power supply 11 always supplies5 VDC and 3 VDC. It should be understood that the power supply 11 maynot be a dedicated power supply for the car navigation device, but maybe a power supply which is used in common by the entire vehicle.

The reference symbol 12 and the reference symbol 13 are power supplieswhich generate 1.8 VDC from the 3 VDC of the power supply 11. The powersupply 12 is a power supply circuit of high capacity which suppliespower to the CPU 1 during the normal power supply ON mode. And the powersupply 13 is a power supply circuit of low capacity which supplies powerto the CPU 1 during the standby mode. The reference symbol 14 is a powersupply circuit which generates 2.5 VDC from the 5 VDC of the powersupply 11.

The reference symbol 15 is a power control circuit which is made up fromlogic circuits. This power control circuit 15 receives a signal(STNDBY_EN) from the CPU 1, and controls the ON-OFF of the powersupplies 12 and 13 and the power switches 16 and 17. The power switch 16receives a signal (SUPPORT_EN) from the power control circuit 15, andcontrols the ON-OFF of the 5 VDC from the power supply 11. And the powerswitch 17 receives the signal (SUPPORT_EN) from the power controlcircuit 15, and controls the ON-OFF of the 3 VDC from the power supply11. The power switches 16 and 17 are made up from mechanical relays orfrom semiconductor switches.

Next the power supplies which are required by the various elements willbe explained. The CPU 1 of this embodiment requires 3 VDC and 1.8 VDC.The flash memory 2, the DRAM 3, and the bus buffer 4 require 3 VDC. TheASIC 5 requires 5 VDC, 3 VDC, and 2.5 VDC. And the present positiondetection device 10, the CD-ROM device 7, and the input device 8 require3 VDC and 5 VDC as necessary.

The CPU 1 of this embodiment is itself endowed with a normal mode(normal operation) and a standby mode (standby operation). The standbymode of the CPU 1 itself will hereinafter be termed the CPU standbymode, in order to differentiate it from the previously described standbymode of the car navigation device. Furthermore, its normal mode willalso hereinafter be termed the CPU normal mode. The CPU normal mode is amode in which the CPU 1 executes a program normally. And the CPU standbymode is a mode in which the CPU 1 itself waits in a low powerconsumption mode and does not execute any program.

When the CPU 1 enters the CPU standby mode the CPU 1 makes the signalSTANDBY_EN ON, and when it returns to the CPU normal mode it makes thesignal STANDBY_EN OFF. When the CPU 1 enters the CPU standby mode, itspower consumption at 3 VDC and at 1.8 VDC becomes extremely small. Forexample, in the case of 1.8 VDC, while in the CPU normal mode theconsumption of electrical current may be about 800 mA, when the CPUstandby mode is entered, it may become about 100 μA. Accordingly, in thestandby mode, the low capacity power supply 13 whose power loss is smallis used as the power supply for the 1.8 VDC of the CPU 1.

When the CPU 1 executes a predetermined command for the CPU standbymode, it enters the CPU standby mode itself. When, in the standby mode,it receives a signal from the outside, it wakes up and returns to theCPU normal mode. In this embodiment, when during the CPU standby modethe signal ACC to the CPU 1 goes to ON, the CPU 1 transits from the CPUstandby mode to the CPU normal mode. However, a different signal may beemployed as the cause for wakeup.

FIG. 2 is a timing chart which shows the manner in which each of thepower supplies is controlled when the CPU 1 transits to the CPU standbymode, and also when it transits to the CPU normal mode upon being wokenup. It should be understood that the explanation of how the CPU 1transits to the CPU standby mode due to the signal ACC, and how it iswoken up and transits to the CPU normal mode, will be provided later.

In the following explanation, the 5 VDC which is outputted from thepower switch 16 will be termed VCC 5VS, the 3 VDC which is outputtedfrom the power switch 17 will be termed VCC _3VS, the 1.8 VDC which isoutputted from the power supply 12 will be termed VCC_1P8P_1, the 1.8VDC which is outputted from the power supply 13 will be termedVCC_1P8P_2, the wired OR power supply of VCC_1P8P_1 and VCC_1P8P_2 willbe termed VCC_1PBP, and the 2.5 VDC which is outputted from the powersupply 14 will be termed 2P5VS. Furthermore, the signal which isoutputted from the power control circuit 15 and which controls the powersupply 12 will be termed EN1P8P_1#, the signal which controls the powersupply 13 will be termed EN1P8P_2#, and the signal which controls thepower switch 16, the power switch 17, and the bus buffer 4 will betermed SUPPORT_EN.

It should be understood that, in the following explanation, when asignal or a power supply has become active it is spoken of as havinggone “ON”, and when a low active signal has become active it also isspoken of as having gone “ON”. Accordingly, in FIG. 2, when a low activesignal as well is ON, they are all shown as high.

When the CPU 1 goes into the standby mode, the signal STANDBY_EN goes ONjust before. When the signal STANDBY_EN goes ON, the power controlcircuit 15 turns the signal SUPPORT_EN to OFF. The signal SUPPORT_EN isset to ON during the CPU normal mode while the signal STANDBY_EN isbeing received, while during the CPU standby mode it is set to OFF. Thepower control circuit 15 turns the signal EN1P8P_2# to ON at almost thesame timing as when the signal SUPPORT_EN goes to OFF, and turns thesignal EN1P8P_1# to OFF after the voltage of the power supply VCC_1P8P_2has stabilized.

The ON-OFF of the power supply 12 is controlled by the ON-OFF of thesignal EN1P8P_1#, and the ON-OFF of the power supply 13 is controlled bythe ON-OFF of the signal EN1P8P_2#. Accordingly, when the CPU standbymode is entered, without fail, after first the power supply 13 has beenturned ON by the signal EN1P8P_2 going ON, then the signal EN1P8P_1#goes OFF and the power supply 12 is turned OFF. By doing this, no noiseis imposed upon the power supply VCC_1P8P due to the switching over. Thetime period after the signal EN1P8P_2# goes ON until the signalEN1P8P_1# goes OFF can be varied to any suitable value within the rangein which no noise is imposed upon the power supply VCC_1P8P due to theswitching over.

The power switch 16 and the power switch 17 receive the signalSUPPORT_EN and output the power supply VCC_5VS and the power supplyVCC_3VS, but, since these power supplies are not used for any structuralelements which must be supplied during the standby mode, no particularproblem will occur whether they are ON or OFF. The bus buffer 4functions as a bus buffer for the exterior when the signal SUPPORT_EN isON, and when the signal SUPPORT_EN goes to OFF it becomes high impedanceand functions to cut off connection to the external circuitry. Due tothis, signals or flows of current from the outside are cut off while thesignal SUPPORT_EN is OFF, in other words during the standby mode.

As above, when, after the CPU 1 has executed the predetermined procedurefor entering the standby mode, the CPU 1 itself enters the CPU standbymode, then the power supply VCC_1P8P to the CPU 1 changes overappropriately from the power supply VCC_1P8P_1 to the power supplyVCC_1P8P_2. Furthermore, the 3 VDC to the CPU 1, the flash memory 2, theDRAM 3, and the bus buffer 4 continues to be supplied just as it is,while, apart from these, the supplies of power to the ASIC 5, thepresent position detection device 10, the CD-ROM device 7, the inputdevice 8, and the other structural elements for which power supply isnot required during the standby mode are all cut off by the power switch16 and the power switch 17. By doing this, the transition of the carnavigation device to the standby mode is completed.

Next, the case in which the CPU 1 returns from the CPU standby mode tothe CPU normal mode will be explained. When the CPU 1 is to return tothe CPU normal mode, the signal STANDBY_EN goes to OFF. When the signalSTANDBY_EN goes to OFF, the power control circuit 15 turns the signalSUPPORT_EN to ON. The power control circuit 15 turns the signal 1P8P_1#to ON at almost the same timing as when the signal SUPPORT_EN goes toON, and after the voltage of the power supply VCC_1P8P_1 has stabilized,it turns the signal EN1P8P_2# to OFF.

By doing the above, when the CPU 1 has returned to the CPU normal mode,without fail, after the signal EN1P8P_1# has gone to ON and the powersupply 12 has first been turned ON, then the signal EN1P8P_2# is turnedto OFF and the power supply 13 is turned to OFF. Accordingly, no noiseis imposed upon the power supply VCC_1P8P due to the changeover. Thetime period after the signal EN1P8P_1# goes ON until the signalEN1P8P_2# goes OFF can be varied to any suitable value within the rangein which no noise is imposed upon the power supply VCC_1P8P due to theswitching over.

As above, when the CPU 1 enters the CPU normal mode from the CPU standbymode, the power supply VCC_1P8P to the CPU 1 is appropriately changedover from the power supply VCC_1P8P_2 to the power supply VCC_1P8P_1.Furthermore, the 3 VDC to the CPU 1, the flash memory 2, the DRAM 3, andthe bus buffer 4 continues to be supplied just as it is, while, apartfrom these, the supplies of power to the ASIC 5, the present positiondetection device 10, the CD-ROM device 7, the input device 8, and theother structural elements for which power supply was not required duringthe standby mode are all turned ON by the power switch 16 and the powerswitch 17. After this, the CPU 1 executes certain predeterminedprocessing in order to complete the transition of the car navigationdevice to the power supply ON mode.

It should be understood that, as a variant of the above example, itmight also be contemplated to use the OFF-ON of the power supply VCC_5VSor of the power supply VCC_3VS as a signal for turning the power supply13 ON and OFF. However, when the power supply VCC_5VS or the powersupply VCC_3VS is used for control of the ON and OFF of the power supply13, it becomes difficult to adjust the timing with respect to the OFFand ON of the power supply 12, and there is a possibility that noisewill occure due to the change over. Accordingly, in order accurately tocontrol the timing of the ON and OFF of the power supplies 12 and 13,both of these power supplies are controlled by signals from the powercontrol circuit 15.

In other words, with this embodiment, since the ON-OFF of the powersupply 12 which is used during the normal mode of the CPU 1 and theON-OFF of the power supply 13 which is used during its standby mode areperformed separately by two different signals which are generated by thepower control circuit 15, therefore it is possible to control the ON-OFFof the power supplies 12, 13 positively and moreover accurately.Accordingly, it is also possible reliably to ensure that no changeovernoise is generated in the power supply VCC_1P8P.

Next, the basic operations when the car navigation device transits tothe power supply ON mode and to the standby mode due to operation of theignition key of the vehicle will be explained. FIG. 3 is a figureshowing the relationships between the position of the ignition key andthe signal ACC, the signal IGN, etc. which are inputted to the CPU 1.

When the ignition key is in the LOCK position or in the OFF position,the signal ACC and the signal IGN are both OFF. When the ignition key isturned as far as the ACC position, then the signal ACC goes to ON. Whenthe ignition key is turned as far as the ON position, then the signalIGN goes to ON and the signal ACC continues to be ON. When the ignitionkey is turned as far as the START position, then the signal ACC goes toOFF and the signal IGN continues to be ON. Although the START positionis a position in which the starter motor is rotated, the signal ACC isturned OFF when the starter motor is rotated. When the ignition key isreturned to the ON position after rotation of the starter motor in theSTART position, the signal ACC goes to ON again, and the signal IGNcontinues to be ON. Next, when the engine is to be stopped and theignition key is turned from the ON position as far as the ACC position,although the signal IGN goes to OFF, the signal ACC still maintains itsstate of being ON. Next, when the ignition key is turned as far as theOFF position, the signal ACC also goes to OFF.

Here, the operation during cranking of the vehicle will be explainedwith reference to FIG. 3. When the starter motor is rotated with theignition key in the START position, a high electrical current flows inorder to drive the starter motor. Due to this, the phenomenon appearsthat the electrical potential of the battery drops considerably duringrotation of the starter motor. In this case, since the electricalpotential of the supply of power to the car navigation device alsodrops, this may become a cause of erroneous operation of the carnavigation device. Accordingly, during cranking, it is necessary for thecar navigation device appropriately to transit to the standby mode.

However, although this also depends upon the speed of the rotationaloperation of the ignition key, a time period clearance of only about 100mS is available from when the signal ACC goes to OFF due to the rotationof the ignition key to the START position, to when the starter motoractually starts to rotate. Accordingly, as will be describedhereinafter, it is ensured that a shorter time period is sufficient forthe procedure of transiting to the standby mode during cranking, thanfor the procedure of transiting to the normal standby mode.

By the above, the car navigation device transits from the standby modeto the power supply ON mode by the signal ACC going to ON when startingto use the vehicle, temporarily transits to the standby mode due to thesignal ACC going to OFF with the ignition key in the START position, andagain transits to the power supply ON mode by the signal ACC going to ONafter the rotation of the starter motor has been completed. Next, whenthe use of the vehicle is completed, the car navigation device transitsto the standby mode by the signal ACC going to OFF.

It should be understood that, since the signal ACC and the signal IGNare inputted to the CPU 1, the CPU 1 functions as an ON-OFF detectiondevice which detects a signal for turning the car navigation device ONand OFF (for changing over its power supply mode) in association withoperation of the ignition key of the vehicle. However, it would also beacceptable to detect this signal by a circuit which was separate fromthe CPU 1, and to input a signal carrying the result of this detectionto the CPU 1.

FIG. 4 is a flow chart of the control when the standby mode is entereddue to the signal ACC and the signal IGN. The procedure of FIG. 4 isexecuted by the CPU 1.

In a step S1, a decision is made as to whether or not the signal ACC isOFF. If the signal ACC is OFF then the flow of control proceeds to astep 52, while if it is not OFF then this procedure repeats. In the stepS2, a decision is made as to whether or not the signal IGN is ON. If thesignal IGN is ON then the flow of control proceeds to a step S4, whileif it is not ON then the flow of control proceeds to a step S3. If thesignal IGN is OFF when the signal ACC is also OFF, then the systemtransits to the normal standby mode. On the other hand, if the signalIGN is ON when the signal ACC is OFF, the system transits to the abovedescribed standby mode for during cranking.

In the steps S3 and S4, the procedure is performed for transiting to thestandby mode. In the standby mode in this embodiment, as describedabove, the power supply of the DRAM 3 is backed up, and the contents ofthe DRAM 3 are preserved. Accordingly, it is not necessary to transferthe contents of the DRAM 3 to the flash memory 2 which is the nonvolatile memory. However, when transiting to the standby mode, errorchecking procedures for the DRAM 3 such as check-summing and the likeare performed, as well as the storage of the minimum possible amount ofrequired information and the like.

As described above, although in the transit to the normal standby modethe steps S3 and S4 are processed, in the transit to the standby modeduring cranking only the step S4 is performed, since there is not muchtime available until the power supply drops. Accordingly, procedures areperformed in the step S3 such as, for example, error checking and thelike, which occupy comparatively great amounts of processing time, andin the case of which no great problem will occur even if, in the worstcase, processing is not performed. In the step S4, the necessaryprocedures are performed which absolutely must be executed fortransiting to the standby mode: for example, saving of information suchas stack pointers and the like, saving of status of interruptprocessing, and so on.

In a step S5, the signal STANDBY_EN is turned ON. After this, in a stepS6 a command for the CPU standby mode is executed, and the CPU 1 itselfenters the CPU standby mode. The power control circuit 15 executes theabove described power control sequence due to the signal STANDBY_ENgoing to ON, and the car navigation device is put into the standby mode.

FIG. 5 is a figure showing a flow chart for the processing fortransiting from the standby mode to the power supply ON mode. The CPU 1has a hardware structure such that, when during the CPU standby mode asignal at a predetermined terminal thereof goes to ON, it is capable ofbeing waked up and executing a predetermined program. In thisembodiment, the signal ACC is connected to the predetermined terminal,and the predetermined program is the program of FIG. 5. Accordingly whenthe signal ACC goes to ON due to the operation of the ignition keyduring the standby mode of the car navigation device, in other wordsduring the CPU standby mode of the CPU 1, the program of FIG. 5 startsto operate.

In a step S11 of FIG. 5, the procedures for transiting from the standbymode to the power supply ON mode are performed. For example, checking isperformed as to whether or not the stack pointers and the status ofinterrupt processing agree with the values which were saved during thetransition to the standby mode, and error checking is performed in theDRAM 3 and the flash memory 2, and the like. When the processing of thestep S11 has been completed, this routine terminates, and the carnavigation device enters the normal power supply ON mode.

Since in this manner the contents of the DRAM 3 are ensured to be thesame as the contents before the transition to the standby mode, it isnot necessary to transfer any data from the flash memory 2 or toregenerate any data. Accordingly, upon the signal ACC going to ON, thecar navigation device promptly becomes able to be used in its statebefore the transition to the standby mode

It should be noted that although, in the above described embodiment, theexample of a car navigation device was explained, it is not necessarilylimited by this detail. It could be applied to a computer for on-vehicleuse (a mobile computer), or to any other intelligent terminal foron-vehicle use. In other words, it can be applied to any informationdevice for on-vehicle use which is equipped with a volatile memory suchas a DRAM or the like.

Furthermore, the program of FIGS. 4 and 5 of the above describedembodiment may be supplied as recorded upon a recording medium such as aCD-ROM or the like. Furthermore, it would be possible to endow theinformation device such as a car navigation device or the like with thefunction of being connected to a portable telephone (a mobile telephone)and of thus being connected to the internet, so that it could receivesupply of the program of FIGS. 4 and 5 via the internet.

What is claimed is:
 1. An information device for on-vehicle use, comprising: a CPU which is capable of normal operation and of standby operation which achieves low power consumption; a first power supply for use during the normal operation of the CPU; a second power supply for use during the standby operation of the CPU; and a power control device which performs ON-OFF control of the first power supply and the second power supply, and wherein: the CPU outputs a first signal to the power control device when the CPU transits from the normal operation to the standby operation; the power control device outputs a second signal to the second power supply which turns the second power supply ON when the first signal has been inputted from the CPU, and outputs a third signal to the first power supply which turns the first power supply OFF after a predetermined time period has elapsed after the output of the second signal; the CPU outputs a fourth signal to the power control device when the CPU transits from the standby operation to the normal operation; and the power control device outputs a fifth signal to the first power supply which turns the first power supply ON when the fourth signal has been inputted from the CPU, and outputs a sixth signal to the second power supply which turns the second power supply OFF after a predetermined time period has elapsed after the output of the fifth signal.
 2. An information device for on-vehicle use according to claim 1, further comprising: a DRAM which is employed in the normal operation of the CPU; and a third power supply which supplies power to the DRAM, wherein, when the CPU transits from the normal operation to the standby operation, the third power supply continues to supply power to the DRAM.
 3. An information device for on-vehicle use according to claim 1, further comprising: an ON-OFF detection device which detects a signal for turning the information device for on-vehicle use ON and OFF in association with operation of an ignition key of a vehicle, and wherein: when the ON-OFF detection device has detected a signal to turn the information device for on-vehicle use OFF, the ON-OFF detection device notifies the CPU to an effect that the ON-OFF detection device has detected the signal to turn the information device for on-vehicle use OFF; and the CPU transits to the standby operation after having executed a predetermined procedure for standby.
 4. An information device for on-vehicle use according to claim 3, wherein: when the ON-OFF detection device has detected a signal to turn the information device for on-vehicle use OFF directly before rotation of a starter motor of the vehicle, the ON-OFF detection device notifies the CPU to an effect that the ON-OFF detection device has detected the signal to turn the information device for on-vehicle use OFF directly before rotation of the starter motor of the vehicle; and the CPU transits to the standby operation after only a portion of the procedure for standby has been executed, so that the procedure for standby is completed before starting of rotation of the starter motor of the vehicle. 